Bile secretion is a major hepatic function, vital to the survival of man, yet often impaired in diseases of the liver resulting in cholestasis. The present proposal is a continuation of studies of the mechanism of bile formation initiated during the past five years, supported by USPHA grant # AM 17153 (1974-1978), and focused on the role of liver plasma membrane Na ion, K ion - ATPase in bile acid independent secretion. These studies have led to a more detailed assessment of the biology of bile secretory membranes as follows: 1. Role of Nation, K ion - ATPase and other enzymes in liver plasma membranes enriched in bile canaliculi. A) Histochemical localization of Na ion, K ion -ATPase in hepatocytes and membrane fractions. b) Search for specific marker for bile canalicular membranes. C) Utilization of chlorpromazine as a cholestatic model to further elucidate bile secretory mechanisms; to examine the relationship of chlorpromazine metabolites and inhibition of bile acid independent flow and Na ion, K ion-ATPase, both in vivo in the isolated perfused rat liver, and in vitro in isolated fractions of canalicular membranes. 2. To study how choleretic and cholestatic bile acids influence the structure and function of the "bile secretory membranes" as assessed by biochemical and morphologic techniques (scanning and transmission electron microscopy).